Intelligent And Multifunctional Sofa Bed

ABSTRACT

The invention discloses a sofa bed, comprising: a sofa seat including a bottom frame; a movable frame installed on the bottom frame to reciprocate; a driving device to drive the movable frame to reciprocate; a folding frame rotatably mounted on the movable frame; a first transmission device to drive the rotation of the folding frame, the first transmission device is used to drive the folding frame to be folded to form a rest sofa in a first position; the first transmission device is used to drive the folding frame to unfold to form a rest bed in a second position. The first transmission device drives the folding frame to perform automatic folding, the problem of inconvenient operation is solved. The driving device drives the movable frame to generate high-frequency reciprocating motion, the user can turn on a vibration mode to relax, enriching the functions of the sofa bed and improves the user experience.

CROSS REFERENCE TO PRIORITY APPLICATIONS

This application claims the benefit of Chinese Application 202210435835.4 for an intelligent and multifunctional sofa bed (filed Apr. 24, 2022 at the China National Intellectual Property Administration, CNIPA). The entire contents of above applications are hereby incorporated by reference in their entirety.

FIELD OF THE INVENTION

The invention pertains to the field of sofa bed, particularly to an intelligent and multifunctional sofa bed.

BACKGROUND OF THE INVENTION

A sofa bed is a kind of furniture that can be used as a sofa or a bed, it is more suitable for use when the space is limited. In the prior art, the sofa bed generally needs to manually lift or lower the back cushion to realize the function conversion between a bed and a sofa, the manual folding operation is relatively inconvenient. In addition, the existing sofa bed has a single function, which leads to a poor user experience.

In view of the problem mentioned there is a need for an improved sofa bed which allows for an easy operation.

SUMMARY OF THE INVENTION

The purpose of the invention is to solve the problems in the prior art. In accordance with an aspect of the embodiment, there is provided an intelligent and multifunctional sofa bed, comprising: a sofa seat, the sofa seat includes a bottom frame; a movable frame, the movable frame is installed on the bottom frame for reciprocating motion; a driving device, the driving device is installed on the bottom frame and used to drive the movable frame to reciprocate; a folding frame, the folding frame is rotatably mounted on the movable frame; a first transmission device, the first transmission device is installed on the movable frame and used to drive the rotation of the folding frame, the first transmission device is used to drive the folding frame to be folded on the movable frame to form a rest sofa in a first position; the first transmission device is used to drive the folding frame to unfold beyond the movable frame to form a rest bed in a second position.

Preferably, the sofa bed further includes a weight sensor for triggering the folding frame to fold, the weight sensor is signally connected to the first transmission device via a control unit; when the weight sensor recognizes that the weight is below a set value, the first transmission device drives the folding frame to automatically fold on the movable frame.

Preferably, the sofa bed further includes two limit switches for controlling the rotation path of the folding frame, the limit switch is signally connected to the first transmission device via the control unit; when the folding frame rotates to trigger one of the limit switches, the first transmission device stops working so that the folding frame is folded; when the folding frame rotates to trigger the other limit switch, the first transmission device stops working so that the unfolding of the folding frame is completed.

Preferably, the folding frame includes a first folding frame, a second folding frame and a third folding frame, one end of the first folding frame is pivotally connected to the movable frame, one end of the second folding frame is pivotally connected to the other end of the first folding frame, one end of the third folding frame is pivotally connected to the other end of the second folding frame; in the first position, the first transmission device drives the first folding frame together with the second folding frame and the third folding frame to fold until the first folding frame and the second folding frame are folded and attached together to form a backrest of the rest sofa, the third folding frame is translated onto the movable frame to form a cushion of the rest sofa; in the second position, the first transmission device drives the first folding frame together with the second folding frame and the third folding frame to unfold, the first folding frame, the second folding frame and the third folding frame are co-linear and coplanar to form a rest bed.

Preferably, the sofa bed a first rotating shaft is rotatably installed on the movable frame, one end of the first folding frame is fixedly installed on the first rotating shaft; the first transmission device includes a first motor, the first motor drives the first shaft to rotate.

Preferably, a roller piece is provided at one end of the third folding frame away from the second folding frame, the roller piece is rolled and held on a bearing surface of the bottom frame.

Preferably, the bottom frame is connected with the movable frame via a limiting element, the limiting element includes a first fixed base, a first movable base and a roller assembly; the first fixed base is installed on the bottom frame, the first movable base is movably arranged relative to the first fixed base and is used for installing the movable frame, the roller assembly is rolled between the first fixed base and the first movable base.

Preferably, the driving device includes a second motor installed on the bottom frame, a second rotating shaft rotatably installed on the bottom frame, a first transmission section, and a second transmission section; the second motor drives the second rotating shaft to rotate, the second rotating shaft is provided with an eccentric shaft; one end of the first transmission section is provided with a first shaft hole, the eccentric shaft is adapted to be installed in the first shaft hole; the other end of the first transmission section is connected to one end of the second transmission section, the other end of the second transmission section is connected to the movable frame.

Preferably, the driving device further includes a first transmission shaft rotatably mounted on the bottom frame; one end of the first transmission shaft is provided with a first transmission wheel, the other end is provided with a second transmission wheel; the output end of the second motor is provided with a first driving wheel, the first driving wheel is connected with the first transmission wheel via a belt; one end of the second rotating shaft is provided with a third transmission wheel, the third transmission wheel is connected with the second transmission wheel via a belt.

Preferably, the left and right sides of the bottom frame are respectively provided with a multi-functional portion, the upper end of the multi-functional portion protrudes above the bottom frame, the multi-functional portion forms an armrest of the rest sofa or a guardrail of the rest bed.

Compared with the prior art, the present invention has the following advantages and beneficial effects.

-   -   1. As the movable frame, the driving device, the folding frame         and the first transmission device are provided, the first         transmission device can drive the folding frame to perform         automatic folding, therefore, the problem of inconvenient         operation of the traditional manual folding sofa bed is solved,         and the convenience of use is improved; in addition, the driving         device drives the movable frame to generate high-frequency         reciprocating motion, the user can turn on a vibration mode to         relax the body while resting, which enriches the functions of         the sofa bed and improves the user experience. Meanwhile, the         design of the bottom frame, the movable frame, the driving         device, the folding frame and the first transmission device is         reasonable and ingenious. The vibration mode can be used         regardless of whether the folding frame is opened as a bed or         folded into a sofa. The first transmission device only needs to         drive the folding frame to be folded to realize the state of         being opened as a bed and folded into a sofa. The folding frame         has few parts and light weight, which makes the transmission of         the first transmission device more stable.     -   2. Providing a weight sensor to identify the weight of the         folding frame, after setting the corresponding weight value,         once the user leaves the sofa bed, the folding frame can be         driven by the first transmission device to fold. After the user         leaves the sofa bed, there is no need for the user to manually         fold it to realize automatic folding, which further improves the         convenience of use. Meanwhile, during the folding process of the         folding frame driven by the first transmission device, the         weight is identified by the weight sensor, so as to prevent the         first transmission device from driving the folding frame with         excessive weight to be damaged, thereby improving the service         life of the components.     -   3. The limit switch is provided for identifying the rotation         stroke of the folding frame, which can monitor the specific         position of the folding frame in real time, so as to avoid         excessive folding of the folding frame, thereby further         improving the service life of the components.

BRIEF DESCRIPTION OF THE DRAWINGS

The present invention will become more fully understood from the detailed description given herein below and the accompanying drawings which are given by way of illustration only, and thus are not limitative of the present invention, and wherein:

FIG. 1 is a schematic view of the intelligent and multifunctional sofa bed according to a preferred embodiment of the present invention (unfolded as a sofa bed);

FIG. 2 is a right side view of the intelligent and multifunctional sofa bed according to a preferred embodiment of the present invention (partial structures are omitted);

FIG. 3 is a perspective view of a partial structure of the intelligent and multifunctional sofa bed according to a preferred embodiment of the present invention;

FIG. 4 is a schematic view (partially exploded) of the movable frame, the first transmission device and the first folding frame according to the preferred embodiment of the present invention;

FIG. 5 is a schematic view (partially exploded) of the bottom frame and the driving device of the preferred embodiment of the present invention;

FIG. 6 is an exploded view of the limiting element according to the preferred embodiment of the present invention;

FIG. 7 is a front view (partial structure) of the limiting element according to the preferred embodiment of the present invention;

FIG. 8 is a schematic view of the intelligent and multifunctional sofa bed according to a preferred embodiment of the present invention (in the state of being folded into a sofa);

FIG. 9 is a control chart of the intelligent and multifunctional sofa bed according to a preferred embodiment of the present invention.

DETAILED DESCRIPTION OF THE INVENTION

The invention will be further described below in details with reference to the figures and embodiments.

Please refer to FIG. 1 to FIG. 9 , the specific structure of a preferred embodiment of the present invention is shown, which is an intelligent and multifunctional sofa bed, including a sofa seat 1, a movable frame 2, a driving device 3, a folding frame 4 and a first transmission device 5.

Referring to FIG. 1 , FIG. 2 , FIG. 3 and FIG. 7 , the sofa seat 1 is provided with a bottom frame 11, the movable frame 2 is movably installed on the bottom frame 11, the driving device 3 is installed on the bottom frame 11 and is used to drive the movable frame 2 to reciprocate back and forth in high frequency to generate vibration; the folding frame 4 is rotatably installed on the movable frame 2, the first transmission device 5 is installed on the movable frame 2, and is used to drive the folding frame 4 to rotate, thereby realizing the folding or unfolding of the folding frame 4; the first transmission device 5 is used to drive the folding frame 4 to be folded on the movable frame 2 to form a rest sofa in a first position; the first transmission device 5 is used to drive the folding frame 4 to unfold beyond the movable frame 2 to form a rest bed in a second position. Specifically, as the movable frame 2, the driving device 3, the folding frame 4 and the first transmission device 5 are provided, the first transmission device 5 can drive the folding frame 4 to perform automatic folding, therefore, the problem of inconvenient operation of the traditional manual folding sofa bed is solved, and the convenience of use is improved; in addition, the driving device 3 drives the movable frame 2 to generate high-frequency reciprocating motion, the user can turn on a vibration mode to relax the body while resting, which enriches the functions of the sofa bed and improves the user experience.

Next, the folding frame 4 includes a first folding frame 41, a second folding frame 42 and a third folding frame 43, one end of the first folding frame 41 is pivotally connected to the movable frame 2, one end of the second folding frame 42 is pivotally connected to the other end of the first folding frame 41, one end of the third folding frame 43 is pivotally connected to the other end of the second folding frame 42. In the first position, the first transmission device 5 drives the first folding frame 41 together with the second folding frame 42 and the third folding frame 43 to fold until the first folding frame 41 and the second folding frame 42 are folded and attached together to form a backrest of the rest sofa, and the third folding frame 43 is translated onto the movable frame 2 to form a cushion of the rest sofa; in the second position, the first transmission device 5 drives the first folding frame 41 together with the second folding frame 42 and the third folding frame 43 to unfold, the first folding frame 41, the second folding frame 42 and the third folding frame 43 are co-linear and coplanar to form a rest bed.

The first folding frame 41, the second folding frame 42 and the third folding frame 43 are pivotally connected by setting a pivot at one end and a shaft hole for inserting the pivot at the other end, alternatively, the first folding frame 41, the second folding frame 42 and the third folding frame 43 are connected by hinges. Specifically, one end of the first folding frame 41 is pivotally connected to the upper rear side of the movable frame 2. The first transmission device 5 drives the first folding frame 41 to rotate upward and backward when folded, thereby driving the second folding frame 42 rotates downward and backward, and makes the first folding frame 41 and the second folding frame 42 overlap in the front and rear directions, and the second folding frame 42 drives the third folding frame 43 to move backward and above the movable frame 2. It can be seen that the first folding frame 41, the second folding frame 42 and the third folding frame 43 are ingeniously pivoted, then the folding action is simple and easy to realize. And at least one cushion is provided above the first folding frame 41, the second folding frame 42 and the third folding frame 43.

Furtherly, one end of the third folding frame 43 away from the second folding frame 42 is provided with a roller member that is rolled and held on the bearing surface of the bottom frame 11. The roller member includes a support leg 431 and a roller 432, the support leg 431 is installed on the bottom of the third folding frame 43 and extending downward, the roller 432 is installed at the bottom of the support leg 431. The third folding frame 43 assist its own movement via the roller 432 when folded. On one hand, the smoothness of the movement of the third folding frame 43 during folding is improved, on the other hand, the noise generated when the third folding frame 43 moves is eliminated.

Referring to FIG. 1 , FIG. 2 , FIG. 3 and FIG. 8 , the sofa bed further includes a weight sensor 6, a limit switch 7 and a control unit 8. The weight sensor 6, the limit switch 7 and the first transmission device 5 are respectively connected with the control unit 8 in signal. The weight sensor 6 and the limit switch 7 transmit signals to the control unit 8, the control unit 8 controls the driving device 3 and the first transmission device 5 to work.

Continued, the weight sensor 6 is used to identify the weight of the folding frame 4 and trigger the folding frame 4 to fold. The weight sensor 6 is installed on the movable frame 2. When the weight sensor 6 recognizes that the weight is below the set value, the first transmission device 5 drives the folding frame 4 to automatically fold on the movable frame 2. Specifically, when the folding frame 4 is unfolded into a sofa bed, the first folding frame 41 abuts against the weight sensor 6; when the folding frame 4 is folded into a sofa, the third folding frame 43 abuts against the weight sensor 6. As an example, when the first folding frame 41, the second folding frame 42 and the third folding frame 43 are opened, it is now a sofa bed, the first folding frame 41 abuts against the weight sensor 6, and obtains the weight setting value M1 according to the weight when the first folding frame 41 abuts against the weight sensor 6.

In more detail, once the user sits or places heavy objects on the first folding frame 41, the second folding frame 42 and the third folding frame 43, the first transmission device 5 stops when the weight is greater than the set value M1, in order to prevent the first transmission device 5 from being automatically folded when there is a heavy object on the folding frame 4. In this way, it can be ensured that during the automatic folding process driven by the first transmission device 5, there will be no heavy objects on the folding frame 4, and this design can protect the sofa bed.

Once the user leaves, the weight of the folding frame 4 is below the set value Ml, at this time, the weight sensor 6 will send a signal to the control unit 8, the control unit 8 will control the first transmission device 5 to fold the folding frame 4, so as to realize the function of automatic folding when the user leaves. It should be noted here that the first folding frame 41, the second folding frame 42 and the third folding frame 43 are pivotally connected. As the first folding frame 41, the second folding frame 42 and the third folding frame 43 are unfolded, even when only the first folding frame 41 abuts against the weight sensor 6, the weight of the second folding frame 42 and the third folding frame 43 is transferred to the first folding frame 41 after being unfolded.

Continued, there are two limit switches 7, the two limit switches 7 are signally connected to the first transmission device 5 via the control unit 8. When the folding frame 4 rotates to trigger one of the limit switches 7, the first transmission device 5 stops working so that the folding frame 4 is folded. When the folding frame 4 rotates to trigger another limit switch 7, the first transmission device 5 stops working so that the folding frame 4 completes the folding. Specifically, the limit switch 7 includes a trigger 71 and a sensing piece 72, the trigger 71 is installed on the upper rear side of the movable frame 2, the sensing piece 72 is installed on the rear side of the first folding frame 41. When the first folding frame 41 is rotated to be folded, the sensing piece 72 contacts the trigger 71, the trigger 71 transmits a signal to the control unit 8, the control unit 8 controls the first transmission device 5 to stop working, thereby completing the folding. The principle of triggering to unfold is the same as that of folding, which will not be described here.

Referring to FIG. 4 , a first rotating shaft 21 is rotatably installed on the movable frame 2, one end of the first folding frame 41 is fixedly installed on the first rotating shaft 21, the pivot connection between the movable frame 2 and the first folding frame 41 is realized by the first rotating shaft 21. The first transmission device 5 includes a first motor 51, the first motor 51 is connected to the first shaft 21 and drives the first shaft 21 to rotate. Specifically, the first transmission device 5 also includes a first screw rod 52 and a first gear 53, the first screw 52 is installed at an output end of the first motor 51, the first gear 53 is mounted on the first rotating shaft 21 and is engaged with the first screw rod 52.

Referring to FIG. 1 , FIG. 2 , FIG. 6 and FIG. 7 , the bottom frame 11 is connected to the movable frame 2 via a limiting element 12, the limiting element 12 includes a first fixed base 121, a first movable base 122 , and a roller assembly 123 . The first fixing base 121 is installed on the bottom frame 11, the first movable base 122 is movably arranged relative to the first fixed base 121 and the movable frame 2 is mounted thereon. The roller assembly 123 is installed between the first fixed base 121 and the first movable base 122 in a rolling manner. In the embodiment of the present invention, the roller assembly 123 includes a plurality of large rollers 1231 and a plurality of small rollers 1232. The first fixed base 121 is provided with a first groove 1211 and a second groove 1212, the first movable base 122 is provided with a third groove 1221 and a fourth groove 1222. The first groove 1211 is opposite to the third groove 1221, the plurality of the large rollers 1231 are installed in the first groove 1211 and the second groove 1212. The second groove 1212 is opposite to the fourth groove 1222, the plurality of small rollers 1232 are installed in the second groove 1212 and the fourth groove 1222. The large roller 1231 and the small roller 1232 are made of flexible materials. The moving position of the first movable base 122 is limited by the large roller 1231 and the small roller 1232 for the driving device 3 to drive the movable frame 2 to move up and down and back and forth to generate a vibration effect. The large roller 1231 and the small roller 1232 are used to limit the moving position of the first movable base 122, so that the driving device 3 drive the movable frame 2 to move up and down and back and forth to generate a vibration effect. In addition, the moving distance of the first movable base 122 is smaller than the length of the first fixed base 121, the first movable base 122 move up and down and back and forth in the first fixed base 121 after being installed on the first fixed base 121. Both ends of the first fixed base 121 are installed with a first baffle 1213 for restricting the movement of the first movable base 122 in the front and rear directions.

In addition, the first movable base 122 is installed with a limit screw, the limit screw extends into the second groove 1212 and the fourth groove 1222 to limit the small roller 1232 in order to prevent the small roller 1232 from being disengaged due to the movement of the first movable base 122.

Continued, the steps for installing the limiting element 12 are as follows: Firstly, install the first fixed base 121 on the bottom frame 11, and then insert the first movable base 122 from a free end of the first fixed base 121. Next, install the plurality of the large rollers 1231 in the first groove 1211 and the third groove 1221, and install the plurality of the small rollers 1232 in the second groove 1212 and the fourth groove 1222. Finally, install the first baffle 1213 on two free ends of the first fixed base 121. After the above steps are performed, the movable frame 2 is installed on the first movable base 122. In order to ensure the stable installation of the movable frame 2, there are four limiting structures 12 installed at the four corners of the bottom frame 11.

Referring to FIG. 1 to FIG. 3 , and FIG. 5 , the driving device 3 includes a second motor 31, a second rotating shaft 32, a first transmission section 33 and a second transmission section 34. The second motor 31 is installed on the bottom frame 11. The second rotating shaft 32, the first transmission section 33 and the second transmission section 34 are rotatably mounted on the bottom frame 11. The second motor 31 drives the second rotating shaft 32 to rotate, the second rotating shaft 32 is provided with an eccentric shaft 321. One end of the first transmission section 33 is provided with a first shaft hole 331, the eccentric shaft 321 is fitted to the first shaft hole 331. The other end of the first transmission section 33 is connected to one end of the second transmission section 34, the other end of the second transmission section 34 is connected to the movable frame 2. Specifically, the first transmission section 33 and the second transmission section 34 are fixedly connected, the second transmission section 34 and the movable frame 2 are also fixedly connected. The eccentric shaft 321 of the second rotating shaft 32 is fitted to the first shaft hole 331, when the second rotating shaft 32 rotates, the first transmission section 33 is driven to move up and down and back and forth regularly, so as to make the movable frame 2 vibrate back and forth and up and down.

Continued, the driving device 3 also includes a first transmission shaft 35 rotatably mounted on the base frame 11. One end of the first transmission shaft 35 is provided with a first transmission wheel 351, the other end is provided with a second transmission wheel 352. The output end of the second motor 31 is provided with a first driving wheel (not shown), the first driving wheel is connected with the first transmission wheel 351 by a belt. One end of the second rotating shaft 32 is provided with a third transmission wheel 322, the third transmission wheel 322 is connected with the second transmission wheel 352 by a belt. Preferably, the diameter of the first transmission wheel 351 is larger than the diameter of the second transmission wheel 352, so as to achieve deceleration and make the movable frame 2 vibrate more vigorously and more smoothly.

Besides, the left and right sides of the bottom frame 11 are respectively provided with a multi-functional portion 13, the upper end of the multi-functional portion 13 protrudes above the bottom frame 11, and the multi-functional portion 13 forms an armrest of the rest sofa or a guardrail of the rest bed.

The above embodiments, which are intended to enable those skilled in the art to understand the content of the disclosure and implement it accordingly, are merely for describing the technical concepts and features of the disclosure, and the scope of patent application of the disclosure cannot be defined only by the embodiments, i.e., any equivalent variations or modifications made in accordance with the spirit disclosed by the disclosure still fall within the scope of claims of the disclosure. 

What is claimed is:
 1. An intelligent and multifunctional sofa bed, comprising: a sofa seat, the sofa seat includes a bottom frame; a movable frame, the movable frame is installed on the bottom frame for reciprocating motion; a driving device, the driving device is installed on the bottom frame and used to drive the movable frame to reciprocate; a folding frame, the folding frame is rotatably mounted on the movable frame; a first transmission device, the first transmission device is installed on the movable frame and used to drive the rotation of the folding frame, the first transmission device is used to drive the folding frame to be folded on the movable frame to form a rest sofa in a first position; the first transmission device is used to drive the folding frame to unfold beyond the movable frame to form a rest bed in a second position.
 2. The sofa bed as defined in claim 1, wherein further includes a weight sensor for triggering the folding frame to fold, the weight sensor is signally connected to the first transmission device via a control unit; when the weight sensor recognizes that the weight is below a set value, the first transmission device drives the folding frame to automatically fold on the movable frame.
 3. The sofa bed as defined in claim 2, wherein further includes two limit switches for controlling the rotation path of the folding frame, the limit switch is signally connected to the first transmission device via the control unit; when the folding frame rotates to trigger one of the limit switches, the first transmission device stops working so that the folding frame is folded; when the folding frame rotates to trigger the other limit switch, the first transmission device stops working so that the unfolding of the folding frame is completed.
 4. The sofa bed as defined in claim 1, wherein the folding frame includes a first folding frame, a second folding frame and a third folding frame, one end of the first folding frame is pivotally connected to the movable frame, one end of the second folding frame is pivotally connected to the other end of the first folding frame, one end of the third folding frame is pivotally connected to the other end of the second folding frame; in the first position, the first transmission device drives the first folding frame together with the second folding frame and the third folding frame to fold until the first folding frame and the second folding frame are folded and attached together to form a backrest of the rest sofa, the third folding frame is translated onto the movable frame to form a cushion of the rest sofa; in the second position, the first transmission device drives the first folding frame together with the second folding frame and the third folding frame to unfold, the first folding frame, the second folding frame and the third folding frame are co-linear and coplanar to form a rest bed.
 5. The sofa bed as defined in claim 4, wherein a first rotating shaft is rotatably installed on the movable frame, one end of the first folding frame is fixedly installed on the first rotating shaft; the first transmission device includes a first motor, the first motor drives the first shaft to rotate.
 6. The sofa bed as defined in claim 4, wherein a roller piece is provided at one end of the third folding frame away from the second folding frame, the roller piece is rolled and held on a bearing surface of the bottom frame.
 7. The sofa bed as defined in claim 1, wherein the bottom frame is connected with the movable frame via a limiting element, the limiting element includes a first fixed base, a first movable base and a roller assembly; the first fixed base is installed on the bottom frame, the first movable base is movably arranged relative to the first fixed base and is used for installing the movable frame, the roller assembly is rolled between the first fixed base and the first movable base.
 8. The sofa bed as defined in claim 1, wherein the driving device includes a second motor installed on the bottom frame, a second rotating shaft rotatably installed on the bottom frame, a first transmission section, and a second transmission section; the second motor drives the second rotating shaft to rotate, the second rotating shaft is provided with an eccentric shaft; one end of the first transmission section is provided with a first shaft hole, the eccentric shaft is adapted to be installed in the first shaft hole; the other end of the first transmission section is connected to one end of the second transmission section, the other end of the second transmission section is connected to the movable frame.
 9. The sofa bed as defined in claim 8, wherein the driving device further includes a first transmission shaft rotatably mounted on the bottom frame; one end of the first transmission shaft is provided with a first transmission wheel, the other end is provided with a second transmission wheel; the output end of the second motor is provided with a first driving wheel, the first driving wheel is connected with the first transmission wheel via a belt; one end of the second rotating shaft is provided with a third transmission wheel, the third transmission wheel is connected with the second transmission wheel via a belt.
 10. The sofa bed as defined in claim 1, wherein the left and right sides of the bottom frame are respectively provided with a multi-functional portion, the upper end of the multi-functional portion protrudes above the bottom frame, the multi-functional portion forms an armrest of the rest sofa or a guardrail of the rest bed. 